Religion is a good example of a solid good reason, even from a human standpoint, for undertaking large projects without a positive expected economic ROI.

And even amongst humans there are many other such factors (ego of the current leader, etc.)

You're also making economic assumptions that might be wrong at an advanced enough level of technology.

A man from the 14th century Americas might understandably believe that

    "the idea of malign intent ignores the physical economic factors that are true everywhere on this planet. The amount of energy it takes to get here from across the Atlantic, and the necessary probability that there is at least one other country with every element we have, in much higher quantities, and closer to them, precludes any motive to wipe us out. Given the effort involved and the alternatives, the only possible reason to contact us is benevolent."

A few generations later, that tribe would no longer be recorded in history, wiped out by war and smallpox brought on ships from across the world.

▲ motohagiography 8 days ago | parent [-]

there are large projects, and then there is interstellar travel. imo they aren't comparable or analogous. comparing it to boats is a kind of linear extrapolation or mapping of those effects to the present, whereas the distance between boats and faster than light craft is a non-linear mapping where all the factors contributing to its development really are different.

the analogy to 14th century Americas would be that aliens arrive, have technology for resource extraction, this disrupts the economics of the existing civilization, which then orients itself to this new technological power and factions compete to dominate brokerage of it among themselves, or to destroy it. the aliens need to secure their resource supply lines from the native factions, and when there is no peace to be had, they fight the way they know how, which wipes most of them out, or they leave and come back in a more evolved millenium.

the cultures that were strong enough to adapt, survived. the ones that weren't able to adapt, died. in a sense it was a case of the meek inheriting the earth, where natives who fought against alien technology lost, and the people in ones that adapted, lived to survive to today.

but the comparison breaks down when you substitute boats for craft capable of relativistic speeds. the sophistication required to do faster than light travel is too high to make unforced errors like that, imo.

	▲	sebastiennight 2 days ago \| parent [-]
		Is there any part of your comment that would not have been applicable as-is in the 14th century based on the known laws of economics and physics in pre-Colombian America? And, from there, is there any reason to believe that we now have perfect understanding of economics and physics, which would warrant the level of absolute certainty you're showing above (despite the fact that such certainty was unwarranted in the past)?